In the electronics industry, a printed circuit board (PCB) is employed to hold and interconnect packaged integrated circuit (IC) devices and other components such as resistive and capacitive elements. The PCBs are composed of alternating layers of conductive and insulating materials. The insulating layers function to electrically isolate each of the conductive layers from one other, and are often composed of a dielectric material. The conductive layers provide the ICs and components on the PCB with a particular voltage. They can also be patterned into signal traces, to transmit signals to and from the ICs inserted on the board. For example, a conductive layer is often employed to provide supply voltages such as 5.0 volts or 3.3 volts. A conductive layer may also be used as a ground plane.
The edge of the PCB functions as a type of connector which is plugged into a conductive slot connecting it to external power supplies or other PCBs.
The IC devices inserted on a given board determine the voltage supply requirements for that board. For instance, if all of the ICs on a PCB are designed with a 5.0 volt bipolar device technology, then the PCB is designed with 5.0 volt supply and ground voltage planes. Currently, the trend in IC device technology and design is to reduce power consumption by designing the logic portion of an IC with smaller low power devices having lower voltage supply requirements and designing the input/output (I/O) driver portion of the IC with larger high power devices having higher voltage supply requirements. One example of this type of technology is the BiCMOS device technology. A circuit designed with BiCMOS device technology typically utilizes CMOS devices requiring a 3.3 volt supply and bipolar devices requiring a 5.0 volt supply.
Since PCBs are designed to accommodate the voltage requirements for the ICs employed with them, it is often necessary to redesign PCBs when new generations of a given IC are developed. In particular, when a processor device, such as the central processing unit (CPU) of a computer system, is upgraded, the I/O pins and voltage requirements of the CPU often change. As a result, the PCB must also be redesigned to accommodate the upgraded processor.
The present invention is a method that minimizes redesign of a PCB due to changes in voltage requirements of the devices that are used with it.